1. Technical Field
The present invention is directed generally toward integrated circuit capacitor structures. More particularly, the present invention relates to a method and apparatus for passivating inductively coupled surface currents under metal-insulator-metal capacitor structures.
2. Description of the Related Art
Capacitor structures metal layers that are formed above a semiconductor device. IC capacitor structures cause concern with inductively and capacitively coupled substrate surface currents. Inductively coupled surface currents may exist during high speed switching operations. At slower speeds or direct current (DC) bias or DC bypass, capacitively coupled surface currents may exist due to large capacitor structures. Such currents lessen the quality factor (Q) for a device and can cause latch-up and other failures on a chip. The “Q” of a device, in this case, is a measure of how good the capacitor is. If surface currents caused by a capacitor are detrimental to an IC device, then the “Q” will be unacceptable.
Surface currents are most recognized as a problem related to inductors. One solution to inductively coupled surface currents related to inductors is to include floating poly and metal sheets underneath the inductor. The results of floating metal/poly sheets are unknown at this time. Another solution is to use ion implantation and no subsequent annealing over a silicon-on-insulator (SOI) layer to mitigate this effect. SOI is an expensive process and, thus, may be considered disadvantageous for that reason alone.